In recent years, with the advance in an RFID tag technology for managing articles in a non-contacting manner, article management has been increasingly automatized mainly in the business fields such as distribution.
As a conventional technique for article management using RFID tags, Patent Document 1 has been proposed. In Patent Document 1, an RFID tag (hereinafter referred to as “tag”) is given to an article, and devices for reading the tag (hereinafter referred to as “tag readers”) are densely provided in the environment. When an article to be searched is specified by a terminal for performing article search, each tag reader communicates with the tag given to the article. The place of the tag reader receiving a response from the tag is determined as the place of the article searched.
Further, as another conventional technique using RFID tags, Patent Document 2 has been proposed. In Patent Document 2, a tag is given to an article, and tag readers are provided in the environment. In Patent Document 2, an active tag incorporating a power cell, with which a communication distance of from the tag to the tag reader is long, is used in order to provide tag readers thinly, and by using the intensities of radio waves from the tag received by a plurality of tag readers, the position of the article in a space is determined.
On the other hand, as a technique for detecting an object moved or left by a human by using images (difference between frames), Non-Patent Document 1 has been proposed.
In Non-Patent Document 1, it is assumed that body movement is continuously performed from the time a human starts moving an article until he/she finishes the moving, and that frames in which differences between frames are not less than a threshold in moving images are continued. In other words, an increase and a decrease in a difference area between frames are regarded as a start and an end of an event that a human moves an article. Then, a difference between an image before starting the moving event and an image after the moving event ends saved as background images is calculated to thereby identify the article moved.
Further, Patent Document 3 proposes another technique, including an RFID for detecting presence or absence of a human or the like and a camera for recognizing an image. By associating the detection range of the RFID and the imaging range of the camera with each other, traffic of people or the like is analyzed based on information from the RFID and the camera, and the analyzed information is distributed.
Patent Document 1: Japanese Laid-Open Patent Publication No. 07-146362
Patent Document 2: Japanese Laid-Open Patent Publication No. 2000-357251
Patent Document 3: Japanese Laid-Open Patent Publication No. 2005-011057
Non-Patent Document 1: “Detection of object moved or left by a human,” by Takashi Watanabe et al., issued on Mar. 7, 2005, Proceedings of the 2005 IEICE General Conference, D-12-37, pp. 187